This invention relates to an exhaust gas purifying device for a marine engine and, more particularly, to an improved catalytic gas exhaust treatment arrangement for such an engine.
It is well known that exhaust gases from an internal combustion engine may be treated by a system that includes a catalyst that will cause a chemical reaction to occur that renders certain of the exhaust gas constituents harmless. In connection with such arrangements, it is conventional to position the catalyst in such a manner that it is contained within the exhaust system or an exhaust passage of the engine. Such placement is desirable to ensure treatment of the exhaust gases. However, the support of the catalyst bed in such a location presents numerous problems. One of these problems has to do with the actual heat which the supporting element must encounter in such an arrangement. Not only are the exhaust gases hot, but the catalyst must operate at an elevated temperature in order to achieve the desired reaction. As a result, the thermal stresses on the supporting arrangement for the catalyst bed can cause either looseness and leakage or, alternatively, can put compressive forces on the catalyst and catalyst bed that can cause damage to it.
It is, therefore, a principal object of this invention to provide an improved arrangement for treating the exhaust gases in an internal combustion engine with a catalyzer.
It is a further object of this invention to provide an arrangement for cooling the supporting arrangement for the catalyzer bed of an internal combustion engine exhaust treatment system.
The treatment of the exhaust gases from an internal combustion engine is particularly important with outboard motors. As is well known, such outboard motors normally discharge their exhaust gases into the atmosphere back through the body of water in which the outboard motor is operating. As such, it is particularly important to remove from the exhaust gases materials which would pollute the water in which the watercraft is operating.
In the copending applications entitled "Oil Remover For Exhaust Gas of Marine Propulsion Unit", Ser. No. 871,516, Filed June 6, 1986 in the name of Tomio Iwai, now U.S. Pat. No. 4,735,046, issued Apr. 5, 1988 and entitled "Exhaust Gas Purifying Device For Marine Engine", Ser. No. 5,603, filed Jan. 21, 1987, in the name of Masanori Takahashi now U.S. Pat. No. 4,772,236, issued Sept. 20 1988, both of which are assigned to the assignee of this application, there are disclosed very effective arrangements for treating the exhaust gases of an outboard motor. In connection with certain embodiments shown in these applications, there is a catalyst bed that is supported within an opening of the engine which is in proximity to the exhaust ports for treatment of the exhaust gases. In accordance with such an arrangement, it is particularly advantageous if the mounting arrangement for the catalyst can be effectively cooled.
It is, therefore, a still further object of this invention to provide an improved arrangement for cooling the catalyst mounting arrangement in such an arrangement.